Treatment of patients with locally advanced or recurrent adenocarcinoma of the rectum continues to represent a challenge to oncologists. Currently, standard therapy involves a course of preoperative radiation to doses between 45 and 60 Gray. Recently 5-fluorouracil has been used as a radiation enhancing agent for patients with rectal carcinoma, with good clinical results. Hydroxyurea is another agent which has been used for radiosensitization, primarily for tumors of the head and the neck. This approach has not been used for carcinomas of the rectum. This study evaluates escalating doses of hydroxyurea with standard dose radiation therapy 5040cGy. Patients are evaluated for response and toxicity. Following chemo-radiotherapy, patients undergo standard surgical procedures with further treatment decided upon by the investigators.